Pneumatic press

ABSTRACT

A pneumatic press has a piston and cylinder mounted between an upper mounting plate and a ram plate for driving the latter downwardly. An exhaust valve controls flow of air from the cylinder through a large exhaust opening in the upper mounting plate to atmosphere. Air under pressure is trapped in a chamber provided between the piston and the exhaust valve upon closing of the exhaust valve to preload the piston for the succeeding operation. Such air pressure in conjunction with spring-biased means holds the exhaust valve closed until their force is exceeded by the force of a mechanical actuator movable with the piston.

United States Patent [72] Inventor John F. Reeves [56] References Cited 1 A l N Exa UNITED STATES PATENTS [2 1 P 3,450,037 6/1969 Lickliteretal. 100/266 x [22] 3 478 678 11/1969 1; kl't 1 1 100/266 x [45] Patemed Aug. 17,1971 1c 1 ere a. [73] Assignee Robert Paul Lickliter and Earl Abbott P ma y x m ne -W lli m ce Hamburg, N.Y. Attorney-Christel & Bean ABSTRACT: A pneumatic press has a piston and cylinder mounted between an upper mounting plate and a ram plate for driving the latter downwardly. An exhaust valve controls flow [54] of air from the cylinder through a large exhaust opening in the g upper mounting plate to atmosphere. Air under pressure is [52] U.S. Cl 100/53, trapped in a chamber provided between the piston and the ex- 100/257, 100/266, 100/269 haust valve upon closing of the exhaust valve to preload the [51] Int. Cl Bb 1/38, piston for the succeeding operation. Such air pressure in con- B30b 15/ i6 junction with spring-biased means holds the exhaust valve Field of Search l00/26 closed until their force is exceeded by the force of a mechani- 266, 257, 53 cal actuator movable with the pistom V W 22 I 7%- l 730 32 30H 94' 720 30 6 70 96 I 20 22 22 74 00 20. Q I I l 70 I 5v 1 y 62 7? I I 6' 0 66 J g I J 86 4 PATENTEU AUDI 7 I971 SHEET 1 OF 3 INVENTOR.

JOHN F REEVES ATTORNEYS.

PATENTEnAusmsn 3,599,561

' sum 2 ur 3 INVENTOR. JOHN F. REEVES ATTORNEYS.

PATENTED AUG] 7 l97| SHEET 3 OF 3 !\l\ I NTUR JOHN F. REEVES ATTORNEY-53 PNEUMATIC PRESS BACKGROUND OF THE INVENTION This invention relates to a pneumatic press and, more particularly, to a new and improved pneumatic press incorporating a valving arrangement for preloading the cylinder with air pressure and for rapidly evacuating air pressure from said cylinder.

Certain known presses include a ram plate mounted for vertical sliding movement on a plurality of vertical guideposts upstanding from a stationary bed, the ram plate and stationary bed defining a die set area therebetween. The upper ends of the guideposts are secured to an upper plate for maintaining the guideposts in vertical alignment thereby permitting free sliding movement of the ram plate. In some recent developments, the ram plate is fluid actuated by a piston and cylinder arrangement to drive the ram plate downwardly into the die set area, the ram plate being mechanically returned by springs or the like. Because of the large diameter pistons employed in these fluid actuators, a large volume of fluid under pressure is required to efficiently actuate these pistons. Conventional three-way control valves are unsatisfactory for controlling efficient rapid actuation of such pistons because of considerable blow by in such valves when shifting between exhaust and operative positions. It has been found that more fluid is lost due to blowby than is lost in exhausting the pressure fluid to atmosphere during piston retraction. Also, a certain time elapses during which pressure builds up to the level required to move the piston on the downstroke, thereby producing a lagging and inconsistent ram plate response to the actuating control. Accordingly, overall press operation time is increased and variations in work in the die set area are introduced. Also, it is desirable to instantaneously exhaust the pressure in the cylinder for rapid cyclic operation of the press.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic press having means for preloading the actuating cylinder to provide instantaneous response upon the application of additional pressure thereto.

It is another object of this invention to provide a pneumatic press having an improved exhaust valving arrangement for rapidly exhausting air pressure in the actuating cylinder immediately upon completion of the downstroke.

The pneumatic press of the present invention is characterized by a valving arrangement which provides rapid exhaust of air pressure from the actuating cylinder to permit immediate return of the piston upon the completion of the downstroke and which closes the exhaust opening prior to complete depletion of the air pressure to provide an air cushion thereby preloading the cylinder in readiness for the next cycle and eliminating the time-consuming buildup of pressure in the cylinder.

The foregoing and other objects, advantages and characterizing features of the air-actuated press of the present invention are pointed out in detail in the following description of 21 typical embodiment thereof considered in conjunction with v the accompanying drawings depicting the same wherein like reference numerals represent like parts throughout the various views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of the pneumatic press of the present invention;

FIG. 2 is a vertical sectional view of the pneumatic press taken about on line 2-2 of FIG. 1 parts being deleted for ease of illustration; 7

FIG. 3 is a vertical cross-sectional view, on a reduced scale, illustrating an operative position of the piston just prior to the opening of exhaust valve;

FIG. 4 is a view similar to FIG. 3 illustrating the open position of the exhaust valve, with parts added to more clearly show the structure of the press of FIG. 1; and FIG. 5 is a fragmentary, vertical sectional view illustrating the means for adjusting the stroke of the ram plate.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing, and particularly to FIGS. 1 and 4, there is shown an illustrative embodiment of the pneumatic press of the present invention comprising a stationary bed 10, a plurality of vertically extending guideposts 12 suitably fixed at their lower ends to bed 10, a ram head plate 14 vertically slidable on guideposts l2 and defining a die set area 16 with bed 10, and an upper mounting plate 18 slidably adjustable on guideposts l2. Guideposts 12 extend upwardly from bed 10 through suitable bores and bushings in ram plate 14 and mounting plate 18. A plurality of upstanding threaded posts 20 are threaded at their lower ends into bed 10 and extend upwardly through openings in ram plate 14 and mounting plate 18, the former being freely movable relative to posts 20 and the latter being secured to posts 20 adjacent their upper ends between nuts 22 to adjustably fix the height of mounting plate 18 above bed 10.

Bed 10 and plates 14 and 18 are preferably rectangular in plan form and can be formed of steel plating. Track members 24 and 26 are suitably secured on the undersurface of ram plate 14 and on the upper surface of bed plate 10, respectively, and are adapted to receive the upper and lower dies of the usual die set, not shown. However, it should be understood that the press of this invention is not restricted to use with die sets, but has general utility in varied applications.

Ram plate 14 is suspended below mounting plate 18 by a ram plate return assembly comprising, in the illustrated form, rods 28 suitably fixed at their lower ends to ram plate 14 and passing upwardly through openings in mounting plate 18. The upper end of each rod 28 mounts a washer 30, a nut 32 and a locknut 34, and a compression spring 36 encircles each rod 28 with its opposite ends bearing against washer 30 and the upper surface of mounting plate 18. Ram plate 14 is thus resiliently supported for reciprocating sliding movement on guideposts 12 by springs 36 with downward movement thereof into die set area 16 being against the bias of springs 36 and limited by a plurality of stops 38 vertically adjustably mounted on posts 20 between ram plate 14 and bed plate 10. Stops 38 comprise sleeves 40 threaded on posts 20 and fixed in vertically adjusted position by jam nuts 42 engaging against their undersurfaces. The upper surface of each sleeve 40 has a resiliently deformable cushion 44, preferably formed of rubber, glued or otherwise fixed thereon, for limiting downward movement of ram plate 14 and providing a noiseless initial return thrust to ram plate 14 at the end of its downstroke.

A pneumatically actuated piston and cylinder arrangement is disposed between mounting plate 18 and ram plate 14 to drive the latter downwardly into die set area 16. To this end, press cylinder 50 is suitably secured to the undersurface of mounting plate 18 inwardly of guideposts 12, posts 20 and rods 28 as by capscrews 52 (FIGS. 1 and 2) and is provided with a suitable O-ring seal 54 sealing against mounting plate 18. Cylinder 50 preferably is as large in diameter as can be accommodated between posts 12, 20 and rods 28. A piston 56 is suitably secured to the upper surface of ram plate 14 in vertical registry with cylinder 50 as by capscrews 58 (FIG. 2) and is formed of a heavy material providing considerable inertia to ram plate 14 during its downstroke. The upper edge of piston 56 has a pair of peripheral flanges 60 having a suitable O-ring seal 62 carried therebetween for sealing against the inner surface of press cylinder 50.

The upper surface of piston 56 is cylindrically recessed as at 68 defining a chamber 70 within which is received an exhaust valve, generally designated 72, comprising an upper ring 74 and a lower ring 76 suitably secured together as by screws 78 and clamping therebetween a resiliently yieldable sealing ring 80. A relatively large central exhaust opening 82'is provided in mounting plate 18 and is surrounded by an annular valve seat 84 disposed on the undersurface of mounting plate 18. With piston 56 in the position shown in FIG. 2, sealing ring 80 of ex-' haust valve 72 is in sealing engagement with valve seat 84.

Extending axially through piston 56 and exhaust valve 72 is a rod 86 secured to ram plate 14 by a capscrew 88. Rod 86 moves vertically with piston 56 and relative to exhaust valve 72. An O-n'ng seal 90 (FIG. 2) is carried in an annular groove in exhaust valve 72 to provide a fluidtight seal between exhaust valve 72 and rod 86. Threadably secured to the upper end of rod 86 is an elongated capscrew 92 extending through an exhaust valve actuator 94 in the form of an inverted cup having an annular wall 96 and a bottom wall 98 seated against the upper end of rod 86. Actuator 94 is adapted to open exhaust valve 72 with the free end 100 thereof engaging an annular resiliently yieldable ring 102 surrounding rod.86 and interposed between exhaust valve 72 and actuator 94. An annular disc 104 is supported on actuator 94 and is adapted to trip microswitches 140 and 143 (FIG. 1) for purposes hereinafter explained.

A plurality of washers 106, of varying thicknesses, are slip fitted onto capscrew 92 and are interposed between the head of capscrew 92 and disc 104. These washers 106 can be selectively removed from above actuator 94 and placed adjacent bottom wall 98 of actuator 94 as shown in FIG. to vary the length of stroke of rod 86 prior to the opening of exhaust valve 72 by actuator 94. Also, this adjustment varies the length of stroke of piston 56 and ram plate 14.

Piston 56 is provided with a plurality of bores 110 counterbored as at 112 FIG. 2) for receiving a corresponding number of pins 1 14 having annular enlargements 116 thereon. Annular shoulders 118 are defined between the transition of counterbores 112 to the reduced diameter of bores 110 for limiting upward movement of pins 114. Downward vertical movement of pins 1 14 is limited by the lower ends of pins 1 l4 engagingram plate 14. The lower end of each pin 114 is surrounded by a helical spring 1 l9 seated against ram plate 14 at one end and engaging enlargement 1 16 for urging the pin 1 14 upwardly against the bottom of exhaust valve 72. While preferably four such pins 114 are employed at circumferentially spaced intervals of 90, it should be understood that any required number may be used and spaced in any pattern desired.

Similar, but longer, pins 120 having annular enlargements 122 are provided for engaging the other or top side of exhaust valve 72. Pins 120 are housed in suitable blocks 124 circumferentially spaced about the upper surface of mounting plate 18 and secured thereto by screws 126. Each block 124 is provided with a bore 128 for receiving annular enlargement 122 and a helical compression spring 130 seated at one end against the bottom of bore 128 and abutting annular enlargement 122 at the other end for urging pin 120 downwardly against exhaust valve 72. Pins 120 extend downwardly through openings provided in mounting plate 18 and engage .an annular peripheral rim 132 (FIG. 2) extending upwardly from lower ring 76 of exhaust valve 72. While three such pins 20 are provided in the illustrative embodiment of FIGS. 1 and 2, it should be appreciated that any required or desired number can be used.

It will be appreciated that the diameter of piston 56' is very large providing a substantial area on the upper surface of piston 56 against which air entering press cylinder 50 can react whereby low-pressure air can provide a considerable force. Also, the large lateral dimension of the piston and cylinder arrangement and the direct connection thereof to the ram and mounting plate, respectively, maintain ram plate 14 in accurate vertical slidable registry on guideposts 12 without undue friction therebetween.

An inlet opening (FIG. 1) is provided in mounting plate 18 and communicates with the interior of cylinder 50 for admitting air under pressure into cylinder 50. A control valve,

v as follows:

schematically illustrated in FIG. 1 and identified by reference numeral 138, preferably of the two-way type, is employed for controlling the admission of air under pressure into cylinder 50. Control valve 138 is provided with a conduit 139 connected to a suitable source of air under pressure (not shown) and is connected to inlet 136 by means of a conduit 133. Control valve 138 has only two positions, one for admitting the flow of air under pressure into cylinder 50 and the other for interrupting such flow. It has been found that when conventional three-way or four-way control valves are used to control the admission of air under pressure into a cylinder and the exhaust of air from the cylinder, a considerable amount of pressure is lost through blowby in shifting the valve from pressure to exhaust or vice versa. Not only does this waste pressure but also results in erratic and lagging piston and ram plate response. Accordingly, the provision of a two-way control valve 138 which is operable only to admit and interrupt pressure flow in conjunction with a separate exhaust valve operative to open or close a separate large exhaust opening eliminates the above deficiencies and permits rapid and instantaneous operation of the ram plate piston. Of course, a threeor four-way control valve can be employed provided that all ports except the pressure inlet and outlet be plugged.

A control switch 140, secured to a mounting bracket 142 secured to mounting plate 18 and electrically connected to control valve 138 by conductor 137, is positioned to be engaged by disc 104 in its upward travel to shift control valve 138 for admitting air under pressure into cylinder 50. On downward movement of disc 104, another switch 143, connected to control valve 138 by conductor 135, is actuated to shift control valve 138 to a position interrupting the flow of air pressure into cylinder 50. Thus, only two control switches are incorporated in the present invention to admit or block pressure flow into cylinder 50, the exhaust valve being actuated by mechanical elements as hereinafter described.

It should be appreciated that in employing control switches, a certain time interval, although only of microsecond duration, is inherent between the actuation of the control switch and the response of its control function. The pneumatic press of the present invention does not rely on such electrical switching components to actuate the exhaust valve and accordingly, obviates all of the disadvantages attendant therewith. I

With reference to FIGS. 2, 3 and 4 of the drawings, the mode of operation of the pneumatic press of this invention is Referring to FIG. 2, piston 56 is shown in its uppermost position with the upper central surface thereof slightly spaced below exhaust valve 72. A certain amount of air pressure exists in chamber 70, as will hereinafter become apparent. The combined force of pressure acting against the effective area of the underside of exhaust valve 72 and the bias of springs 119 urging pins 114 against the underside of exhaust valve 72 is v greater than the force of pins biased against the upper side of exhaust valve against seat 84 closing exhaust opening 82.

Upon the admission of air pressure into chamber 70 through opening 136, piston 56 immediately moves downwardly to drive ram plate 14 downwardly. Piston 56 moves downwardly carrying along with it actuator 94 which bears against resilient ring 102 compressing the same and transmitting a downward force acting on the upper side of exhaust valve 72. Piston 56 continues to move downwardly relative to lower pins 114 and reaches the position shown in solid lines in FIG. 3 wherein annular enlargements 116 abut shoulders 118 while upper pins 120 remain engaged with the upperside of exhaust valve 72 by means of springs 130. At this position of piston 56, disc 104 engages control switch 143 and actuates the same to shift control valve 138 to interrupt the flow of air pressure into cylinder 50. At this point, the net force produced by the air pressure against the underside of exhaust valve 72 and the spring biased pins 114 is approximately equal to the net downward force of the now bulging, compressed ring 102 transmitted by actuator 94 and the spring-biased pins 120. FIG. 3 illustrates the relative position of the various components just prior to exhaust valve 72 popping open.

Although the air pressure supply is interrupted, piston 56 is moved further downwardly slightly below the position shown in FIG. 3 by inertia. Corresponding movement of actuator 94 further compresses ring 102 forcing exhaust valve 72 off seat 84 allowing air pressure to be exhausted from cylinder 50, around exhaust valve 72, and through exhaust opening 82 to atmosphere. Exhaust valve 72 is moved downwardly to the position shown in FIG. 4 by upper spring-biased pins 120 and by compressed ring 102 which returns to its normal uncompressed state against the reduced pressure acting on the underside of exhaust valve 72. Downward movement of exhaust valve 72 is limited by the engagement of the lower ends of pins 1 14 with ram plate 14.

As piston 56 reaches the bottom of its downstroke as shown in FIG. 4, it immediately returns upwardly by means of mechanical return springs 36, stop cushions 44 and the rapid exhaust of air pressure through the large exhaust opening 82. As piston 56 moves upwardly carrying along with it ram plate 14, rod 86 and actuator 94, exhaust valve '72 also moves upwardly by the stronger force of the spring-biased pins 114 acting against the smaller force of the spring-biased pins 120. Exhaust valve 72 moves upwardly until sealing ring 80 engages valve seat 84 closing off exhaust opening 82. At this point piston 56 continues to be raised a slight amount compressing the air in chamber 70 until it has reached its uppermost position shown in FIG. 2. During this last movement of piston 56, disc 104 trips control switch 140 to actuate control valve 138 to supply air pressure into inlet 136 and cylinder 50 to initiate another cycle of ram plate 14.

A significant feature of this invention resides in trapping a certain amount of air under pressure in chamber 70 between the closing of exhaust valve 72 and the complete return of piston 56. Such pressure serves to maintain exhaust valve 72 seated and also to preload cylinder-50 in readiness for the next cycle of operation. By preloading cylinder 50, no time is lost in building the pressure up to the level at which piston 56 begins to move downwardly. With the initial admission of air pressure into cylinder 50, piston 56 starts to move downwardly instantaneously. Thus, the pneumatic press of the present invention is instantaneously responsive to control commands for rapid and consistent operation. This rapid and consistent operation is enhanced by the elimination of all but two control switches to eliminate time delays inherent in a plurality of switching operations. With some modification, the exhaust control of the present invention could be adapted for use in a pneumatic press having an inlet control to the cylinder of the type disclosed in application Ser. No.'744,898, filed July 15, 1968 now US. Pat. No. 3,478,678 and assigned to the same assignee as the instant application.

From the foregoing, it is apparent that the objects of the present invention have been fully accomplished. As a result of this invention, an improved pneumatic press of a simple and rugged design is provided for instantaneously actuating a ram headplate in an improved and more efficient manner. Lagging and erratic ram plate response is eliminated by preloading the cylinder prior to the admission of additional air pressure thereto. Also, instantaneous response is realized by the elimination of co; trol switches which inherently introduce time delays in control functions.

A preferred embodiment of this invention having been disclosed in detail, it is to be understood that this has been done by way of illustration only.

I claim:

1. An air-actuated press comprising: a bed; a ram plate guided for movement relative to said bed; a mounting plate on the side of said ram plate opposite said bed; a fluid cylinder mounted on said mounting plate; a piston movable in said cylinder and mounted on said ram plate; an opening in said mounting plate surrounded by a seating surface; an exhaust control valve means disposed in said cylinder in controlling relation to said openin and means within said cylinder biasing said exhaust contro valve means against said seating surface and maintaining said exhaust control valve means spaced from said piston.

2. An air-actuated press according to claim 1 wherein said control valve means comprises a resiliently yieldable seal clamped between a pair of plates and adapted to engage said seating surface of said mounting plate.

3. An air-actuated press according to claim 1 including a chamber defined between said control valve means and said piston and wherein said biasing means includes residual air under pressure in said chamber acting against said control valve means.

4. An air-actuated press according to claim 1 wherein said biasing means includes pins mounted in said piston movable relative thereto and spring means urging said pins against said control valve means.

5. An air-actuated press according to claim 4 including bias means for urging said control valve means away from said seating surface.

6. An air-actuated press according to claim 1 including an actuator for unseating said control valve means and means connecting said actuator to said piston for axial movement therewith.

7. An air-actuated press according to claim 6 wherein said connecting means comprises a rod secured at one end to said ram plate and extending through said piston and said opening.

8. An air-actuated press according to claim 6 including a resiliently yieldable ring disposed on said rod between said actuator and said control valve means.

9. An air-actuated press according to claim 6 wherein said rod is provided with a threaded extension at the other end for adjustably mounting said actuator thereon.

10. An air-actuated press according to claim 6 including adjusting means mounted on said rod for varying the length of stroke of said ram plate.

11. An air-actuated press according to claim 10 wherein said adjusting means comprise a plurality of washers of varying thicknesses selectively positioned on said rod on opposite sides of said actuator.

12. An air-actuated press comprising a bed, ram plate means guided for reciprocating movement toward and away from said bed, mounting plate means on the side of said ram plate means opposite said bed, a cylinder mounted on said mounting plate means between said mounting and ram plate means, a piston movable in said cylinder and mounted on said ram plate means, means for admitting air into said cylinder under pressure to extend said piston and drive said ram plate toward said bed, means for exhausting air from said cylinder during return of said piston, said last-named means including an exhaust control valve, and means closing said exhaust valve means as said piston approaches the end of its return movement to trap air under pressure in said cylinder as said piston completes its return movement and thereby preload said piston for its next extension movement.

13. An air-actuated press according to claim 12 together with means responsive to the return movement of said piston said exhaust valve means is closed to actuate said means for admitting air into said cylinder under pressure to repeat the cycle in a timed relationship. 

1. An air-actuated press comprising: a bed; a ram plate guided for movement relative to said bed; a mounting plate on the side of said ram plate opposite said bed; a fluid cylinder mounted on said mounting plate; a piston movable in said cylinder and mounted on said ram plate; an opening in said mounting plate surrounded by a seating surface; an exhaust control valve means disposed in said cylinder in controlling relation to said opening; and means within said cylinder biasing said exhaust control valve means against said seating surface and maintaining said exhaust control valve means spaced from said piston.
 2. An air-actuated press according to claim 1 wherein said control valve means comprises a resiliently yieldable seal clamped between a pair of plates and adapted to engage said seating surface of said mounting plate.
 3. An air-actuated press according to claim 1 including a chamber defined between said control valve means and said piston and wherein said biasing means includes residual air under pressure in said chamber acting against said control valve means.
 4. An air-actuated press according to claim 1 wherein said biasing means includes pins mounted in said piston movable relative thereto and spring means urging said pins against said control valve means.
 5. An air-actuated press according to claim 4 including bias means for urging said control valve means away from said seating surface.
 6. An air-actuated press according to claim 1 including an actuator for unseating said control valve means and means connecting said actuator to said piston for axial movement therewith.
 7. An air-actuated press according to claim 6 wherein said connecting means comprises a rod secured at one end to said ram plate and extending through said piston and said opening.
 8. An air-actuated press according to claim 6 including a resiliently yieldable ring disposed on said rod between said actuator and said control valve means.
 9. An air-actuated press according to claim 6 wherein said rod is provided with a threaded extension at the other end for adjustably mounting said actuator thereon.
 10. An air-actuated press according to claim 6 including adjusting means mounted on said rod for varying the length of stroke of said ram plate.
 11. An air-actuated press according to claim 10 wherein said adjusting means comprise a plurality of washers of varying thicknesses selectively positioned on said rod on opposite sides of said actuator.
 12. An air-actuated press comprising a bed, ram plate means guided for reciprocating movement toward and away from said bed, mounting plate means on the side of said ram plate means opposite said bed, a cylinder mounted on said mounting plate means between said mounting and ram plate means, a piston movable in said cylinder and mountEd on said ram plate means, means for admitting air into said cylinder under pressure to extend said piston and drive said ram plate toward said bed, means for exhausting air from said cylinder during return of said piston, said last-named means including an exhaust control valve, and means closing said exhaust valve means as said piston approaches the end of its return movement to trap air under pressure in said cylinder as said piston completes its return movement and thereby preload said piston for its next extension movement.
 13. An air-actuated press according to claim 12 together with means responsive to the return movement of said piston said exhaust valve means is closed to actuate said means for admitting air into said cylinder under pressure to repeat the cycle in a timed relationship. 